AlanJW Posted March 19, 2016 Share #1 Posted March 19, 2016 Advertisement (gone after registration) Under Auto ISO settings there is an entry for "Floating ISO". Can someone please explain what that is and when one might use it? Quote Link to post Share on other sites More sharing options...
Advertisement Posted March 19, 2016 Posted March 19, 2016 Hi AlanJW, Take a look here Floating ISO?. I'm sure you'll find what you were looking for!
thighslapper Posted March 19, 2016 Share #2 Posted March 19, 2016 (edited) page 202 of the manual ...... Floating ISO is intended for use with zoom lenses with varying full stops. When set to ON, it can compensate their changing effective apertures while zooming in the following situations: –– in manual exposure control mode –– ISO is set to one of the values, i.e. not to Auto ISO Clear as mud, isn't it ...... I assume it means if you set exposure correctly and then zoom from 24mm at 2.8 to 90mm ...... which forces you to f4 ..... you would have an underexposed photo ..... so this function automatically adjusts ISO to compensate Edited March 19, 2016 by thighslapper 3 Quote Link to post Share on other sites More sharing options...
AlanJW Posted March 19, 2016 Author Share #3 Posted March 19, 2016 page 202 of the manual ...... Floating ISO is intended for use with zoom lenses with varying full stops. When set to ON, it can compensate their changing effective apertures while zooming in the following situations: –– in manual exposure control mode –– ISO is set to one of the values, i.e. not to Auto ISO Clear as mud, isn't it ...... I assume it means if you set exposure correctly and then zoom from 24mm at 2.8 to 90mm ...... which forces you to f4 ..... you would have an underexposed photo ..... so this function automatically adjusts ISO to compensate Perhaps it is my advancing age, but I must have skipped over this when I read the SL Manual (yes I am one of those who actually reads the Manual but I found it impenetrable in some places; I may have to go back and try again). I thank you for the explanation. Perhaps it would be better for Leica to call it "Zoom ISO". I am not a German speaker, and I wonder if the German version is clearer. Quote Link to post Share on other sites More sharing options...
pico Posted March 19, 2016 Share #4 Posted March 19, 2016 It is confusing. Red Camera has a floating ISO feature that they call FLUT, but it is entirely different. By default, RED interprets the set ISO through a lookup table of integers, while FLUT is calculated in real time to floating point numbers. That is quite a feat, but their camera is large enough to include the floating point processor. What is not clear is what Red writes to raw, but I digress. Quote Link to post Share on other sites More sharing options...
Steve Spencer Posted March 19, 2016 Share #5 Posted March 19, 2016 It seems clear to me, because it is a variable aperture zoom when you zoom in the aperture gets narrower. If you are not in floating ISO then to compensate and keep a good exposure the camera uses a slower shutter speed. When you are in floating ISO, however, the camera compensates for the narrower aperture when you zoom in by raising the ISO instead of lowering the shutter speed. I suppose this could be useful to some people in some situations. It is irrelevant to how I shoot, but I am sure some people will like it. Quote Link to post Share on other sites More sharing options...
scott kirkpatrick Posted March 20, 2016 Share #6 Posted March 20, 2016 I shoot only with manual lenses, and I leave floating ISO ON (why not?). I have noticed that when I am bumping along at close to minimum shutter speed, still at near minimum ISO, I get shots in which the camera has chosen values of ISO which are slightly above 50 and shutter speeds a little faster than, say, 1/50 (with a 24mm lens). My experience with auto ISO in other cameras has been that as the light available dims with aperture fixed at the lens, the shutter speed decreases to the minimum and only then does the ISO increase. The SL seems to have a somewhat mixed strategy. I might try some more controlled experiments, e.g. with Floating ISO OFF, but not today. scott Quote Link to post Share on other sites More sharing options...
jrp Posted July 30, 2016 Share #7 Posted July 30, 2016 Advertisement (gone after registration) I think that it may also work in the photo bracketing mode, where ISO is varied, rather than shutter speed. Quote Link to post Share on other sites More sharing options...
Michael Geschlecht Posted July 30, 2016 Share #8 Posted July 30, 2016 (edited) Hello Everybody, Some 20th Century exposure compensation systems alternated 1 shutter speed adjustment with 1 aperture adjustment. Perhaps this is some sort of variant of this alternating 1 shutter speed adjustment with 1 ISO adjustment in some situations. Best Regards, Michael Edited July 30, 2016 by Michael Geschlecht Quote Link to post Share on other sites More sharing options...
ramarren Posted July 30, 2016 Share #9 Posted July 30, 2016 I did a bit of testing with Floating ISO some time back. It is only useful with a dedicated lens set to maximum aperture and a fixed ISO setting in M exposure mode. With, say, the SL24-90 lens, as you zoom from 24 to 90 mm and your initial setting was f/2.8 @ ISO 50, the SL will float the ISO up to ISO 100 in order to accommodate the loss of one stop in lens speed over the zoom range. Not a dramatic benefit to most uses, but handy if you do that sort of thing a lot. 1 Quote Link to post Share on other sites More sharing options...
DTM Posted July 30, 2016 Share #10 Posted July 30, 2016 This is for shooting in "Manual Exposure " mode. In P, A and S modes the camera will adjust for changes in aperture or speed. In M mode where aperture and speed are manually selected the ISO must change when the lens is zoomed from f2.8 to f4 (or reverse) to provide correct exposure. Auto ISO does this for manual lenses (M and R) in Manual exposure mode when the aperture is changed on the lens or speed on the camera. On manual lenses the camera doesn't know the true aperture only the amount of light being received on the sensor so Auto ISO makes the adjustments accordingly. Floating ISO has no affect with manual lenses. 1 Quote Link to post Share on other sites More sharing options...
rriley Posted July 30, 2016 Share #11 Posted July 30, 2016 Based on the lack of clarity in the SL documentation and on the comments here, I would say that a controlled experiment is warranted. Quote Link to post Share on other sites More sharing options...
DTM Posted July 30, 2016 Share #12 Posted July 30, 2016 (edited) I did a bit of testing with Floating ISO some time back. It is only useful with a dedicated lens set to maximum aperture and a fixed ISO setting in M exposure mode. With, say, the SL24-90 lens, as you zoom from 24 to 90 mm and your initial setting was f/2.8 @ ISO 50, the SL will float the ISO up to ISO 100 in order to accommodate the loss of one stop in lens speed over the zoom range. Not a dramatic benefit to most uses, but handy if you do that sort of thing a lot. I think you are exactly correct. I don't see how this is not clear. It is what the manual says. If you don't shoot in full M mode it has no effect. If you do and don't want the camera to adjust leave it off. Edited July 30, 2016 by DTM Quote Link to post Share on other sites More sharing options...
ramarren Posted June 27, 2017 Share #13 Posted June 27, 2017 I think you are exactly correct. I don't see how this is not clear. It is what the manual says. If you don't shoot in full M mode it has no effect. If you do and don't want the camera to adjust leave it off. Per later discussion on another thread, it's primary benefit is for video capture where you want to use manual exposure control and work with an SL zoom shot from one end of the zoom range to the other without the exposure shifting at the wide open aperture setting. For that use, it works very effectively indeed. I've become more interested in the motion capture aspects of the SL. I'm still a newbie with regard to SL settings and features for motion capture, but I can see a lot of potential in it. I'm more used to doing motion capture with single focal length, manually controlled lenses, but zooms net another level of versatility in this work. It's become obvious to me that Leica did a lot of subtle work with the SL body and zooms to make them useful in this context. It's quite conceivable to me that some of the bulk of the SL zooms came from designing them to have a very constant T-stop through the zoom range and excellent parfocal characteristics for use with motion capture. Quote Link to post Share on other sites More sharing options...
Irakly Shanidze Posted June 28, 2017 Share #14 Posted June 28, 2017 This feature is meant for video. If you shoot stills only, Auto ISO is what you want, provided the fully manual mode is not your thing. In video, when the ISO is constant, zooming in a variable maximum aperture lens results in darkening of the scene, and vice versa. Floating ISO mode takes care of it by automatically adjusting ISO to keep the exposure constant. When shooting video, the shutter speed should not be altered, as it has to be 1/2 of the frame rate. Hence the only way to compensate for the transmission loss: changing the ISO. Quote Link to post Share on other sites More sharing options...
scott kirkpatrick Posted June 28, 2017 Share #15 Posted June 28, 2017 I've started working with a TL 11-23 f/3.5 - 4.5 zoom lens for shooting video on the SL, since it covers the area from which the 8 MPx of 4K video is extracted. (It does a fine job on still images as well.) My objective was to see if the auto functions would support a "Vertigo" sort of shot in which you zoom continuously on a figure moving away or towards you, keeping them constant in size while the background scale changes in a disorienting way. This might be possible using M mode, fixed shutter speed, open aperture (or fixed aperture) and Floating ISO (or Auto ISO). There's a problem, at least with the TL lens. The optical zoom is smooth and continuous, but the ISO changes, which require digital communication with the lens, seem to be occurring in steps, not continuously. Also, the lens doesn't seem to be parfocal, as few still camera zoom lenses are. Here's a test with an object at a fixed distance, zooming, at a medium aperture: https://www.flickr.com/gp/133969392@N05/Dhik75 and at open aperture: https://drive.google.com/file/d/0B_DOXbFeLaWibDF2VHpwLVk5NUU/view?usp=sharing In each case, initial focus was obtained with AF, which may have drifted off for reasons known only to the AF software. So this is really only a quick'n dirty test of the exposure corrections. Could someone try this with the SL's 24-90? scott Quote Link to post Share on other sites More sharing options...
Irakly Shanidze Posted June 28, 2017 Share #16 Posted June 28, 2017 24-90 does it perfectly well. As to 11-23 T, it should be parfocal. how do you do it? are you starting zoomed in and then zooming out? Quote Link to post Share on other sites More sharing options...
Irakly Shanidze Posted June 28, 2017 Share #17 Posted June 28, 2017 Scott, I looked at the flickr example. Try to do it the other way around: zoom in first and then zoom out. Focus should stay the same. I am surprised that floating ISO works erratically... I can't see any problem with 18-56 T Quote Link to post Share on other sites More sharing options...
mike3996 Posted July 27, 2020 Share #18 Posted July 27, 2020 (edited) Bumping this thread with a question. First of all, I've been having some GAS about Leica SL. Maybe finally biting the bullet because the alternative is to wait for an M with new EVF system. Can take years. Not to mention SLs are pretty affordable compared to M10P/M10R/eventual M11. I read about the Floating ISO. This feature is genius because from my use of M I've become comfortable shooting Manual exposure, and a zoom lens with variable aperture would foil that thing up. Not that there are variable-aperture zooms for M but anyway. I like the fact that I control the "EC" by choosing to open/close my aperture or shutter speed, or ISO. Okay, the question: the new Panasonic Lumix 20-60 mm lens is a variable-aperture zoom. Does SL (601) support floating ISO with this 3rd-party lens? Edited July 27, 2020 by mike3996 Quote Link to post Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.